Pessimism as a worldview is inherently irrational, and therefore a waste of both your and my time.
Humanity is self-serving; men want what makes them happy, and the vast majority of choices are made with the intention of predicating and fostering happiness. Rationally, it is best then for one to consciously make choices with the intent of creating happiness for oneself.
Pessimism, as an outlook on life, is the view that everything will or does have negative consequences. It is seeing the worst side of everything. It is directly opposite Optimism, which is the view that everything will or does have positive consequences. Optimism is seeing the positive side of everything. For purposes of this discussion, nebulous worldviews such as "realism" will be disregarded.
Since pessimism is seeing the unfavorable side of things, and leads to unfavorable feelings, it does not promote happiness.
Some might argue that pessimism allows them to be happy - that it fosters such low expectations that anything positive is encountered with greater joy than otherwise. However, this is incoherent and contradictory - it is feeling optimistic about pessimism.
Since pessimism does not promote happiness, it does nothing to further the ultimate goal of all men, and is therefore for all realistic purposes an obstacle to happiness.
Given that it is an obstacle to happiness, and that happiness is man's ultimate goal, pessimism should be avoided by those who wish to live happy lives, e.g. all of humanity.
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This is an example of why people over a year removed from any formal logic course should avoid trying to create syllogisms.
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But I still think I'm right.